The present invention relates to lids used for covering cups of the type having an annular brim extending around the mouth thereof, especially plastic lids attachable to disposable paper or plastic cups.
It is conventional to provide disposable cups with disposable plastic lids, especially cups employed in eating establishments where beverages are carried from the serving area by the customer for consumption within or outside of the establishment. The cup, which can be formed of paper, thermo formed plastic, injection molded plastic injection blow-molded plastic, or foamed plastic, for example, typically has a radially outwardly projecting annular (non-helical) bead extending around the cup mouth.
As depicted in FIGS. 1 and 2, one conventional type of lid 10A has a generally flat center portion 12A and a skirt 14A extending downwardly from an outer periphery of the center portion. The skirt includes a radially inwardly projecting annular restriction ring 16A which defines an opening of a diameter d smaller than the outside diameter of the lid brim and cup brim. Accordingly, when the lid is pressed onto the cup, the restriction ring is cammed outwardly by the cup brim and then snaps back to a position beneath the brim to secure the lid to the cup. Since the cup may be subjected to considerable handling by servers and customers after being filled and capped, it is necessary that the lid remain in place even when the cup is jarred or falls over.
It will thus be appreciated that it would be desirable to maximize the retention capabilities of the lids without making the lids more difficult to strip or remove from a molding apparatus.